1. Field of the Invention
The present invention relates to a light source device incorporated in an exposure apparatus for usc in the manufacture of a panel of a cathode ray tube (referred to hereinafter as a xe2x80x9cCRTxe2x80x9d). More particularly, the invention relates to a light source device capable of intercepting light such as reflected or scattered light which results in uneven exposure to reduce uneven exposure, thereby achieving high-quality exposure.
2. Description of the Background Art
A phosphor screen on the inner surface of a panel of a CRT for use as a display monitor and the like has a black matrix (referred to hereinafter as a xe2x80x9cBMxe2x80x9d) produced using resist exposure, and a three-color phosphor pattern produced using direct exposure.
FIG. 11 is a plane view (with a vertical section taken along the line I-II of an enlarged part) for illustrating a structure of the phosphor screen formed on a CRT panel 70 by using an exposure apparatus. In FIG. 11, the reference numeral 701 designates a BM for providing clear separation between phosphors to enhance an image quality; and 702, 703 and 704 designate red-emitting (R), green-emitting (G) and blue-emitting (CB) phosphors, respectively, which are formed in stripe-shaped configuration in predetermined positions of openings of the BM 701.
The phosphor screen shown in FIG. 11 is formed in the steps of forming the BM 701 by a lift-off method using resist exposure, and repeating for R, G and B in any order the process of applying a photosensitive phosphor material, e.g., for G to the inner surface of the panel on which the BM 701 is formed to leave phosphor stripes, e.g. green-emitting phosphor stripes, in the predetermined positions of the openings of the BM 701 by direct exposure and development processes.
FIG. 12 is a cross-sectional view of an exposure apparatus for use in the manufacture of the CRT panel 70 shown in FIG. 11. In FIG. 12, the reference numeral 1 designates a light source device; 20 designates a light control filter; 40 designates a wedge lens; 50 designates a correction lens; and 60 designates a mask. Light emitted from the light source device 1 passes through the light control filter 20, the wedge lens 40 and the connection lens 50 onto the mask 60. The resultant shadow of the mask 60 is projected onto the inner surface of the CRT panel 70, whereby a predetermined pattern is exposed to light.
FIG. 13 is a enlarged view of a portion indicated by the arc C1 of FIG. 12, and illustrates paths of light beams passing through the mask 60 in detail. With reference to FIG. 13, light of a predetermined color or predetermined wavelength which is emitted from the light source device 1 impinges upon the inner surface of the CRT panel 70 in stripe-shaped configuration conforming to the openings of the mask 60.
FIG. 14 is a vertical sectional view of the conventional light source device 1 for use in the exposure apparatus shown in FIG. 12 In FIG. 14, the reference numeral 11 designates a rod-shaped mercury light source having a light emitting region extending linearly in the x-direction; 12 designates a light source slit for partially intercepting light emitted from the mercury light source 11 to restrict an apparent light source configuration, and having a centrally located opening for allowing light to pass therethrough; and 13 designates a Light source housing for holding the mercury light source 11 in its interior space by using O-rings 16. The interior space of the light source housing 13 (having an opening in its upper surface part) in the vicinity of the light emitting region of the mercury light source 11 is filled with a coolant 17 for cooling the mercury light source 11. The reference numeral 14 designates an optical window having a lower surface for contact with the upper surface part of the light source housing 13 having the opening, with one of the O-rings 16 therebetween, to confine the coolant 17 within the interior space of the housing 13 and to direct the light from the mercury light source 11 through an upper surface thereof into the atmosphere. Additionally, the light source housing 13 includes an inlet and an outlet both not shown of the coolant 17, and discharges the coolant 17 through the outlet while feeding the coolant 17 through the inlet into the interior space of the housing 13 at a pressure not less than atmospheric pressure, thereby maintaining constant the temperature of the coolant 17 in the light source housing 13. Thus, since the pressure in the interior space of the light source housing 13 filled with the coolant 17 is always higher than the atmospheric pressure, the optical window 14 is held by an optical window retainer 15 applying a pressure from the atmosphere toward the upper surface part of the light source housing 13, with the O-ring 16 therebetween. The optical window retainer 15 has a centrally located opening 15H which is circular in cross section (which is a section parallel to an xy plane), and is screw-held to the housing 13 by means of a threaded groove not shown formed in the light source housing 13.
In the conventional light source device constructed as above described, it is essential that the optical window retainer is provided on the atmosphere side of the optical window. This presents a problem to be described below.
Detailed consideration of one light profile on the inner surface of the CRT panel being exposed to exposure light emitted from the light source device provides a distribution as shown in FIG. 15. It will be understood from FIG. 15 that a pattern width changes depending on the level of illuminance. In other words, when a component other than a predetermined light distribution is superimposed on the illuminance distribution of the exposure light, the distribution of the pattern width within the panel surface shows unevenness corresponding to the superimposed component.
Tracking a light beam emitted from the mercury light source 11 of FIG. 14 and passing through the inside of the coolant 17 and the optical window 14 into the atmosphere provides a light path as shown in FIG. 16. As illustrated in FIG. 16, a light beam 91 generated in a linear light emitting region 111 of the mercury light source 11 and travailing in the region 111 at an angle xcex8i passes through the wall of a synthetic quartz tube 112 surrounding the light emitting region 111 at an angle xcex8j and then through the coolant 17 and the optical window 14 at angles xcex80 and xcex81 respectively, and emerges into the atmosphere at an outgoing angle xcex8. The ranges of the angles xcex8i, xcex8j, xcex80, xcex81 and xcex8 of the respective light beams 91 to 95 are calculated below. The angle xcex8i of the light beam 91 emitted from the light emitting region 111 is less than a maximum of xc2x190xc2x0 (See Expression (1)) since a light beam having an angular component ranging from 0xc2x0 to less than 90xc2x0 can pass through the synthetic quartz tube 112. The maximum value of the angle xcex8j of the light beam 92 in the synthetic quart tube is xc2x142.70xc2x0 (See Expression (2)), and the maximum value of the angle xcex80 of the light beam 93 in the coolant 17 is xc2x148.28xc2x0 (See Expression (3)). The maximum value of the angle xcex81 of the light beam 94 in the optical window 14 is xc2x142.70xc2x0 (See Expression (4)). The maximum value of the angle xcex8 of the light beam 95 in the atmosphere outside the optical window 14, which equals the angle xcex8i in the light emitting region 111 as a result of calculation, is less than xc2x190xc2x0 (See Expression (1)). That is, the light beam 93 emitted from the mercury light source 11 at the angle of xc2x148.28xc2x0 at the maximum spreads out up to an approximately xc2x190xc2x0 outgoing angle xcex8 in the atmosphere outside the optical window 14.
xe2x80x830xe2x89xa6|xcex8|=|xcex8i|xe2x89xa690xc2x0
                    0        ≤                  "LeftBracketingBar"                      θ            j                    "RightBracketingBar"                ≤                              sin                          -              1                                ⁡                      (                                                            n                  t                                                  n                  s                                            ⁢              sin              ⁢                              xe2x80x83                            ⁢                              θ                                  i                  ⁢                                      xe2x80x83                                    ⁢                  max                                                      )                          ≈                  42.70          ⁢          xc2x0                                    (        2        )            
where n1=1 is the refractive index of air, ng=1.47454 is the refractive index of synthetic quartz, and xcex8i max=90xc2x0.                     0        ≤                  "LeftBracketingBar"                      θ            o                    "RightBracketingBar"                ≤                              tan                          -              1                                (                      1                                                            n                  w                  2                                -                1                                              )                ≈                  48.28          ⁢          xc2x0                                    (        3        )            
where nw=1.33974 is the refractive index of water.                     0        ≤                  "LeftBracketingBar"                      θ            1                    "RightBracketingBar"                ≤                              sin                          -              1                                ⁡                      (                          1                              n                g                                      )                          ≈                  42.70          ⁢          xc2x0                                    (        4        )            
where ng=1.47454 is the refractive index of synthetic quartz.
Because of the light path in the conventional light source device as described above, the light beam 95 emerging from the optical window 14 at an outgoing angle of approximately 90xc2x0 impinges upon an opening wall surface 15HS of the optical window retainer 15, and the opening wall surface 15HS in turn serves as a secondary light source to generate reflected or scattered light 96. The reflected or scattered light 96 is superimposed upon the exposure light which reaches the inner surface of the CRT panel directly from the mercury light source 11 to cause an uneven illuminance distribution. This uneven illuminance distribution leads to an uneven pattern width of the black matrix (BM) and an uneven pattern width of the subsequently generated R, G and B phosphors because of the cause-and-effect relation described with reference to FIG. 15, resulting in the decreased quality of the phosphor screen.
A first aspect of the present invention is intended for a light source device incorporated in an exposure apparatus for use in manufacturing a cathode ray tube panel. According to the present invention, the light source device comprises a light source; a light source housing configured to hold the light source therein; an optical window configured to cause light from the light source to emerge into the atmosphere; an optical window retainer configured to fix the optical window to the light source housing; and a shielding plate placed over the optical window and the optical window retainer and having an opening wall surface extending inwardly beyond an opening wall surface of the optical window retainer to a position overlying the optical window, wherein an upper surface edge portion of the opening wall surface of the shielding plate is positioned in a region including and outside an optical path of outgoing light emerging from the optical window into the atmosphere at a predetermined angle, and wherein the optical window retainer is positioned in a region including and outside a boundary line passing through a position of a lower surface edge portion of the opening wall surface of the shielding plate and having a line-symmetrical relation to the optical path of the outgoing light.
Preferably, according to a second aspect of the present invention, in the light source device of the fist aspect, the upper surface edge portion of the opening wall surface of the shielding plate is positioned on the optical path of the outgoing light.
Preferably, according to a third aspect of the present invention, in the light source device of the first aspect, the upper surface edge portion of the opening wall surface of the shielding plate is positioned outside and near the optical path of the outgoing light.
Preferably, according to a fourth aspect of the present invention, in the light source device of the first aspect, an edge portion of the opening wall surface of the optical window retainer in contact with an upper surface of the optical window is set at a position on the boundary line.
Preferably, according to a fifth aspect of the present invention, in the light source device of the fourth aspect, the opening wall surface of the optical window retainer is a surface perpendicular to the upper surface of the optical window.
Preferably, according to a sixth aspect of the present invention, in the light source device of the fourth aspects the opening wall surface of the optical window retainer is a tapered surface extending along the boundary lie.
Preferably, according to a seventh aspect of the present invention, in the light source device of the first aspect, the predetermined angle is a usable angle of light defined as a maximum angle of direct light emerging from the optical window into the atmosphere and to be used for exposure.
According to an eighth aspect of the present invention, an exposure apparatus comprises the light source device as recited in the first aspect.
According to a ninth aspect of the present invention, a cathode ray tube panel comprises a phosphor screen manufactured using the exposure apparatus as recited in the eighth aspect.
A tenth aspect of the present invention is intended for a light source device incorporated in an exposure apparatus for use in manufacturing a cathode ray tube panel. According to the present invention, the light source device comprises: a light source; a light source housing configured to hold the light source therein; an optical window configured to cause light from the light source to emerge into the atmosphere; and an optical window retainer configured to fix the optical window to the light source housing and having an opening, wherein an opening wall surface of the optical window retainer has a first edge portion in contact with a surface of the optical window and a second edge portion on the opposite side from the first edge portion, and the second edge portion is positioned in a region including and outside an optical path of outgoing light emerging from the optical window into the atmosphere at a predetermined angle, and wherein the optical window retainer is positioned in a region including and outside a boundary line passing through the second edge portion and having a line-symmetrical relation to the optical path of the outgoing light.
Preferably, according to an eleventh aspect of the present invention, in the light source device of the tenth aspect, the second edge portion is positioned on the optical path of the outgoing light.
Preferably, according to a twelfth aspect of the present invention, in the light source device of the tenth aspect the second edge portion is positioned outside and near the optical path of the outgoing light.
Preferably, according to a thirteenth aspect of the present invention, in the light source device of the tenth aspect, the opening wall surface of the optical window retainer is a tapered surface extending along the boundary line.
Preferably, according to a fourteenth aspect of the present invention, in the light source device of the tenth aspect, the predetermined angle is a usable angle of light defined as a maximum angle of direct light emerging from the optical window into the atmosphere and to be used for exposure.
According to a fifteenth aspect of the present invention, an exposure apparatus comprises the light source device as recited in the tenth aspect.
According to a sixteenth aspect of the present invention, a cathode ray tube panel comprises a phosphor screen manufactured using the exposure apparatus as recited in the fifteenth aspect.
In accordance with the first, eighth and ninth aspects of the present invention, in the light source device for the CRT exposure apparatus, the shielding plate of a size determined by a predetermined optical calculation is placed outside the optical window and the optical window retainer is disposed in a position determined by a predetermined optical calculation so that light reflected or scattered from the opening wall surface of the optical window retainer is prevented from reaching an inner surface of the CRT panel. This eliminates the unevenness of an illuminance distribution of exposure light to eliminate the unevenness of a pattern width of a black matrix and the likes, thereby producing the effect of enhancing the quality of the CRT phosphor screen.
In accordance with the tenth, fifteenth and sixteenth aspects of the present invention, the optical window retainer has a configuration defined based on a predetermined optical calculation to prevent light reflected or scattered from the optical window retainer from reaching an inner surface of the CRT panel. This produces the effect of enhancing the quality of the phosphor screen formed on the inner surface of the CRT, similar to the above-mentioned effects.
It is therefore an object of the present invention to overcome a problem with a conventional light source device for an apparatus for exposing an inner surface of a CRT panel, i.e., to suppress the unevenness of an illuminance distribution of exposure light resulting from light reflected or scattered from an opening wall surface of an optical window retainer to eliminate the unevenness of pattern widths of a black matrix and phosphors, thereby improving the quality of a phosphor screen.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.